Multiplexed pressure switch system for an electrically variable hybrid transmission

ABSTRACT

A powertrain has an electrically variable hybrid transmission having an electro-hydraulic control system, plurality of electrical power units, and a plurality of torque transmitting mechanisms selectively engageable by the electro-hydraulic control system to provide four forward speed ranges, a neutral condition, an electric low and high speed mode, an electrically variable low and high speed mode, and a hill hold mode. The electro-hydraulic control system includes a multiplexed pressure switch system. The multiplexed pressure switch system of the present invention allows position detection of six torque transmitting mechanism control valves through the use of only four pressure switches.

TECHNICAL FIELD

The present invention relates to electro-hydraulic control systems forelectrically variable hybrid transmissions.

BACKGROUND OF THE INVENTION

Multi-speed power transmissions, particularly those using planetary geararrangements, require a hydraulic system to provide controlledengagement and disengagement, on a desired schedule, of the clutches andbrakes or torque transmitting mechanisms that operate to establish theratios within the planetary gear arrangement.

These control systems have evolved from substantially pure hydrauliccontrol systems, wherein all of the control signals are produced byhydraulic devices, to electro-hydraulic control systems, wherein anumber of the control signals are produced by an electronic controlunit. The electronic control unit emits electrical control signals tosolenoid valves, which then issue controlled hydraulic signals to thevarious operating valves within the transmission control.

With many of the early pure hydraulic and first generationelectro-hydraulic control systems, the power transmission utilized anumber of freewheel or one-way devices which smooth the shifting orratio interchange of the transmission during both upshifting anddownshifting of the transmission. This relieves the hydraulic controlsystem from providing for the control of overlap between the torquetransmitting mechanism that was coming on and the torque transmittingmechanism that was going off. If this overlap is excessive, the driverfeels a shudder in the drivetrain, and if the overlap is too little, thedriver experiences engine flare or a sense of coasting. The freewheeldevice prevents this feeling by quickly engaging when the torque imposedthereon is reversed from a freewheeling state to a transmitting state.

The advent of electro-hydraulic devices gave rise to what is known asclutch-to-clutch shift arrangements to reduce the complexity of thetransmission and the control. These electro-hydraulic control mechanismsare generally perceived to reduce cost and reduce the space required forthe control mechanism.

In addition, with the advent of more sophisticated control mechanisms,the power transmissions have advanced from two-speed or three-speedtransmissions to five-speed and six-speed transmissions. In at least onepresently available six-speed transmission, just five friction devicesare employed to provide six forward speeds, neutral condition, and areverse speed. Such a gear arrangement is shown in U.S. Pat. No.4,070,927 issued to Polak on Jan. 31, 1978. The use of the planetarygearset shown in the Polak patent has given rise to a number ofelectro-hydraulic control mechanisms, such as that shown in U.S. Pat.No. 5,601,506, issued to Long et al. on Feb. 11, 1997. The torquecapacity of a torque transmitting mechanism (on-coming or off-going)involved in a shift may be conveniently controlled by the combination ofan electrically activated solenoid valve and a pressure regulator valveor trim valve, as disclosed, for example, in the U.S. Pat. No. 5,911,244to Long et al., issued on Jun. 15, 1999, assigned to the assignee of thepresent invention, and incorporated herein by reference. In a typicalsystem, the solenoid valve is activated by pulse-width-modulation (PWM)at a controlled duty cycle to develop a pilot pressure for the pressureregulator valve or trim valve, which in turn, supplies fluid pressure tothe torque transmitting mechanisms in proportion to the solenoid dutycycle.

Additionally, an electrically variable hybrid transmission has beenproposed to improve fuel economy and reduce exhaust emissions. Theelectrically variable hybrid transmission splits mechanical powerbetween an input shaft and an output shaft into a mechanical power pathand an electrical power path by means of differential gearing. Themechanical power path may include clutches and additional gears. Theelectrical power path may employ two electrical power units, ormotor/generator assemblies, each of which may operate as a motor or agenerator. With an electrical storage system, such as a battery, theelectrically variable hybrid transmission can be incorporated into apropulsion system for a hybrid electric vehicle. The operation of suchan electrically variable hybrid transmission is described in the U.S.Pat. No. 6,551,208 to Holmes et al., issued on Apr. 22, 2003.

The hybrid propulsion system uses an electrical power source as well asan engine power source. The electrical power source is connected withthe motor/generator units through an electronic control unit, whichdistributes the electrical power as required. The electronic controlunit also has connections with the engine and vehicle to determine theoperating characteristics, or operating demand, so that themotor/generator assemblies are operated properly as either a motor or agenerator. When operating as a generator, the motor/generator assemblyaccepts power from either the vehicle or the engine and stores power inthe battery, or provides that power to operate another electrical deviceor another motor/generator assembly.

It is important to reliably and inexpensively diagnose torquetransmitting mechanism engagement and disengagement in the abovedescribed torque transmitting mechanism controls, both to verify shiftprogression, and to detect an inadvertent engagement or disengagement.This can be accomplished either indirectly by analyzing the transmissioninput and output speeds, or directly by installing pressure switches ateach of the clutches. However, the diagnostic output with either ofthese techniques is only developed once the respective clutch hasactually started to engage or disengage, which is not especiallydesirable if the engagement or disengagement is inadvertent.Theoretically, one could alternatively measure the pilot pressure or theposition of the trim valve, but such approaches may be expensive toimplement and inaccurate due to the characteristic dithering of a trimvalve.

An effective way to determine a change in the trim valve position is toprovide a pressure sensitive switch in fluid communication with the trimvalve and operable to be selectively pressurized or de-pressurized whenthe trim valve changes position. Traditionally, this method of valvestate diagnostics would require a separate pressure switch for eachvalve, i.e. six pressure switches for six valves. However, packagingspace and cost constraints may make this option unfeasible. Accordingly,what is needed is an inexpensive clutch pressure control arrangementthat provides a reliable diagnostic output early in the clutch pressurecontrol process while relying on a minimum of pressure switches.

SUMMARY OF THE INVENTION

The present invention provides an improved electro-hydraulic controlsystem having a multiplexed (one source controlling multiple functions)pressure switch system for an electrically variable hybrid transmission.The multiplexed pressure switch system of the present invention allowsposition detection of six torque transmitting mechanism control valvesthrough the use of only four pressure switches.

Accordingly, the present invention provides a pressure switch diagnosticsystem for an electrically variable hybrid transmission comprisinghaving a plurality of trim valves each having a first and a secondposition and a plurality of pressure sensitive switches, having a highand a low logic state, each in selective fluid communication with one ofthe plurality of trim valves. Each of the plurality of pressuresensitive switches are operable to detect a change from the first to thesecond position or a change from the second to the first position of itsrespective one of the plurality of trim valves and accordingly each ofthe plurality of pressure switches will report one of the high or thelow logic state. Additionally, at least one logic valve is disposed inselective fluid communication with at least one of the plurality of trimvalves such that at least one of the plurality of pressure sensitiveswitches are operative to detect changes in the at least one logic valvewithout requiring an additional pressure sensitive switch to detect achange in position of the at least one logic valve.

The pressure switch diagnostic system of the present invention mayinclude a first of the at least one logic valve, having a first positionand a second position, disposed in selective fluid communication with afirst and a second of the plurality of trim valves respectively having afirst and second of the plurality of pressure sensitive switches inselective fluid communication therewith. The first and the second of theplurality of pressure sensitive switches being operable to detect achange in position of the first of the at least one logic valve when thefirst of the at least one logic valve moves from the first to the secondposition or from the second to the first position irrespective of theposition of the first and second of the plurality of trim valves.

Additionally, the pressure switch diagnostic system of the presentinvention may include a second of the at least one logic valve, having afirst position and a second position, disposed in selective fluidcommunication with a third of the plurality of trim valves having athird of the plurality of pressure sensitive switches disposed inselective fluid communication therewith. The third of the plurality ofpressure sensitive switches being operable to detect a change inposition of the second of the at least one logic valve from the firstposition to the second position or the second position to the firstposition when the third of the plurality of trim valves is in the firstposition. Alternately, the third of the plurality of pressure sensitiveswitches is operable detect a change in position of the third trim valvefrom the first position to the second position or the second position tothe first position when the second logic valve is in the secondposition.

The plurality of trim valves may be solenoid operated pressure regulatorvalves, while the at least one logic valve may be a multiplex valve. Theplurality of trim valves and the at least one logic valve may beselectively controlled by an electronic control unit. The plurality ofpressure sensitive switches may selectively report the high and the lowlogic state to an electronic control unit.

The present invention also provides a pressure switch diagnostic systemfor an electrically variable hybrid transmission including a first trimvalve, having a first position and a second position, in selective fluidcommunication with a first pressure sensitive switch, wherein the firstpressure sensitive switch is operable to detect and report a change fromthe first to the second position or the second to the first position ofthe first trim valve. Also provided is a second trim valve, having afirst position and a second position, in selective fluid communicationwith a second pressure sensitive switch, wherein the second pressuresensitive switch is operable to detect and report a change from thefirst to the second position or the second to the first position of thesecond trim valve. Also provides is a third trim valve, having a firstposition and a second position, in selective fluid communication with athird pressure sensitive switch, wherein the third pressure sensitiveswitch is operable to detect and report a change from the first to thesecond position or the second to the first position of the third trimvalve. Also provided is a first logic valve, having a first position anda second position, disposed in selective fluid communication with eachof the first trim valve and the second trim valve. Also provided is asecond logic valve, having a first position and a second position,disposed in selective fluid communication with the third trim valve. Thefirst, second, and third trim valves and the first, second, and thirdpressure sensitive switches and the first and second logic valve areconnected in a multiplexed arrangement such that there are fewer of thepressure sensitive switches than the sum of the trim valves and thelogic valves.

The first pressure sensitive switch and the second pressure sensitiveswitch may be operable to detect a change from the first to the secondposition or the second to the first position of the first logic valveirrespective of the position of the first trim valve and the second trimvalve. The third pressure sensitive switch may be operable to detect achange from the first to the second position or the second to the firstposition of the second logic valve when the third trim valve is in thefirst position. Additionally, the third pressure sensitive switch may beoperable to detect a change from the first to the second position or thesecond to the first position of the third trim valve when the secondlogic valve is in the second position.

The first, second, and third trim valves may be solenoid operatedpressure regulator valves, while the first and second logic valve may bemultiplex valves. Each of the first, second, and third trim valves andeach of the first and second logic valves may be selectively controlledby an electronic control unit.

The present invention also provides a pressure switch diagnostic systemfor an electrically variable hybrid transmission including a first trimvalve, having a first position and a second position, in selective fluidcommunication with a first pressure sensitive switch, wherein the firstpressure sensitive switch is operable to detect and report a change fromthe first to the second position or the second to the first position ofthe first trim valve. Also provided is a second trim valve, having afirst position and a second position, in selective fluid communicationwith a second pressure sensitive switch, wherein the second pressuresensitive switch is operable to detect and report a change from thefirst to the second position or the second to the first position of thesecond trim valve. Also provided is a third trim valve, having a firstposition and a second position, in selective fluid communication with athird pressure sensitive switch, wherein the third pressure sensitiveswitch is operable to detect and report a change from the first to thesecond position or the second to the first position of the third trimvalve. Also provided is a fourth trim valve, having a first position anda second position, in selective fluid communication with a fourthpressure sensitive switch, wherein the first pressure sensitive switchis operable to detect and report a change from the first to the secondposition or the second to the first position of the fourth trim valve.Additionally a first logic valve, having a first position and a secondposition, disposed in selective fluid communication with each of thefirst trim valve and the second trim valve and a second logic valve,having a first position and a second position, disposed in selectivefluid communication with the third trim valve are provided.

The first pressure sensitive switch and the second pressure sensitiveswitch are operable to detect a change from the first to the secondposition or the second to the first position of the first logic valveirrespective of the position of the first trim valve and the second trimvalve. The third pressure sensitive switch is operable to detect achange from the first to the second position or the second to the firstposition of the second logic valve when the third trim valve is in thefirst position. Alternately, the third pressure sensitive switch isoperable to detect a change from the first to the second position or thesecond to the first position of the third trim valve when the secondlogic valve is in the second position.

The first, second, third, and fourth trim valves may be solenoidoperated pressure regulator valves, while the first and second logicvalve may be multiplex valves. The first, second, third, and fourth trimvalves and the first and second logic valve may be selectivelycontrolled by an electronic control unit.

The above features and advantages and other features and advantages ofthe present invention are readily apparent from the following detaileddescription of the best modes for carrying out the invention when takenin connection with the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic representation of a electrically variable hybridvehicular powertrain for use with the present invention;

FIGS. 2 a and 2 b is a schematic representation describing theelectro-hydraulic control system utilized with the powertrain of FIG. 1,depicting the control system in an electrical power ON, neutral mode ofoperation;

DESCRIPTION OF THE PREFERRED EMBODIMENTS

Referring to the drawings wherein like characters represent the same orcorresponding parts throughout the several views, there is seen in FIG.1 a powertrain 10 having an engine 12, an electrically variable hybridtransmission 14, and a conventional final drive 16.

The engine 12 is a conventional internal combustion engine. Theelectrically variable hybrid transmission 14 includes a planetary geararrangement having an input shaft 18, an output shaft 20, threeplanetary gearsets 22, 24, and 26, four torque transmitting mechanismsC1, C2, C3, and C4, and an electro-hydraulic control system 28. Thetorque transmitting mechanisms C2 and C4 are conventional fluid-operatedrotating clutch-type devices, while the torque transmitting mechanismsC1 and C3 are conventional fluid-operated stationary clutch or brakedevices. The selective engagement and disengagement of the torquetransmitting devices is controlled by an electro-hydraulic controlsystem 28, which is shown in FIGS. 2 a and 2 b.

Further incorporated into the electrically variable hybrid transmission14 is a pair of electrical power units 30 and 32 that are controlled bya conventional electronic control unit 34. The electronic control unit34 is connected with the electrical power unit 30 through a pair ofelectrical conductors 36 and 38, and is connected with the electricalpower unit 32 through a pair of electrical conductors 40 and 42. Theelectronic control unit 34 is also in electrical communication with anelectrical storage device 44, which is connected with the electroniccontrol unit 34 through a pair of electrical conductors 46 and 48. Theelectrical storage device 44 is generally one or more conventionalelectrical batteries.

The electrical power units 30 and 32 are preferably motor/generatorunits, which, as is well known, can operate as a power supplier or as apower generator. When operating as a motor or power supplier, theelectrical power units 30 and 32 will supply power to the electricallyvariable hybrid transmission 14. When operating as generators, theelectrical power units 30 and 32 will take electrical power from thetransmission, and the electronic control unit 34 will either distributethe power to the electrical storage device 44 and/or distribute thepower to the other power unit, which will be operating as a motor atthat time.

As is well known in electrical controls of power transmissions, theelectronic control unit 34 receives a number of electrical signals fromthe vehicle and transmission, such as engine speed, throttle demand,vehicle speed, to name a few. These electrical signals are used as inputsignals for a programmable digital computer, which is incorporatedwithin the electronic control unit 34. The computer is then effective todistribute the electrical power as required to permit the operation ofthe electrically variable hybrid transmission 14 in a controlled manner.

The planetary gear arrangement, as shown in FIG. 1, provides fourforward speed ratios or ranges between the input shaft 18 and the outputshaft 20. In the first forward range, the torque transmitting mechanismsC1 and C4 are engaged. In the second forward range, the torquetransmitting mechanisms C1 and C2 are engaged. In the third forwardrange, the torque transmitting mechanisms C2 and C4 are engaged. In thefourth forward range, the torque transmitting mechanisms C2 and C3 areengaged. The gearing also provides a neutral condition when the torquetransmitting mechanisms C1, C2, C3 and C4 are disengaged. Additionally,a hill hold condition is provided wherein the torque transmittingmechanism C1 is engaged and C3 is in trim. An electrically variable lowmode of operation is provided wherein the torque transmitting mechanismC1 is engaged, and an electrically variable high mode of operation isprovided wherein the torque transmitting mechanism C2 is engaged. Thepowertrain 10 may also operate in a purely electric mode. The engineoff, electric low speed mode of operation is facilitated by engaging theC1 torque transmitting mechanism. Whereas, the engine off, electric highspeed mode of operation is facilitated by engaging the C2 torquetransmitting mechanism. The powertrain 10 also has two speed ranges ofdrive-home capabilities within the electrically variable hybridtransmission 14 in the event that the electro-hydraulic control system28 undergoes a malfunction or discontinuance of electrical power. In theelectrical power off drive home modes, the electro-hydraulic controlsystem 28 defaults to an electrically variable low mode of operationwherein the torque transmitting mechanism C1 is engaged, and anelectrically variable high mode of operation wherein the torquetransmitting mechanism C2 is engaged.

The electro-hydraulic control mechanism 28 includes an electroniccontrol unit (ECU) and a hydraulic control unit (HYD). The ECUincorporates a conventional digital computer that is programmable toprovide electrical signals to the hydraulic portion of theelectro-hydraulic control system 28 to establish the engagement anddisengagement of the torque transmitting mechanisms C1, C2, C3, and C4.FIGS. 2 a and 2 b show the electro-hydraulic control system 28 ingreater detail. As shown in FIGS. 2 a and 2 b, the hydraulic portion ofthe electro-hydraulic control mechanism 28 includes a hydraulic pump 50,such as a variable volume type pump, that draws fluid from the reservoir52 for delivery to a main passage 54. The main passage 54 is in fluidcommunication with a conventional line regulator valve 56, a check valve58, a line pop-off valve 60, an actuator feed regulator 62, amotor/generator A cooling valve 64, and a motor/generator B coolingvalve 66.

The line pop-off valve 60 is operable to vent pressurized fluid withinthe main passage 54 to the exhaust should an over pressurized conditionmanifest within the main passage 54. The line regulator valve 56establishes the pressure within the main passage 54, and when thatpressure is satisfied, fluid is delivered through a passage 68 to aconventional cooler 70. A cooler bypass valve 72 is in fluidcommunication with the passage 68 and provided in parallel with thecooler 70. The cooler bypass valve 72 is operable to provide fluid flowthrough passage 68 in the event that fluid passage through the cooler 70is blocked. The fluid from the cooler 70 and/or cooler bypass valve 72will pass through a lubrication regulator valve 74 for distribution to alubrication system 75 of the electrically variable hybrid transmission14.

The actuator feed regulator 62 reduces the pressure within the mainpassage 54 to a control pressure in passages 76 and 78. The fluid inpassage 78 is communicated to a solenoid valve 80. The fluid in passage76 is communicated to a plurality of solenoid valves 82, 84, 86, 88, 90,92, and 94. The solenoid valves 90 and 92 are on/off type solenoidvalves, while the solenoid valves 80, 82, 84, 86, 88, and 94 arevariable pressure type solenoid valves. The solenoid valves 86, 88, and94 are normally high or normally open type solenoid valves, while theremaining solenoid valves 80, 82, 84, 90, and 92 are normally low ornormally closed type solenoid valves. As is well known, a normally opensolenoid valve will distribute output pressure in the absence of anelectrical signal to the solenoid.

The solenoid valve 80 is operable to provide an output pressure inpassage 96 that controls the bias pressure or control pressure on eitherthe motor/generator A cooling valve 64 and the motor/generator B coolingvalve 66 or a damper lock-out clutch trim valve 98. The state of amultiplex valve 100 will determine to which valves the pressure withinthe passage 96 is directed. When the multiplex valve 100 is in thepressure set position the pressurized fluid within the passage 96 willbe directed to bias the damper lock-out clutch trim valve 98 via apassage 99. The damper lock-out clutch trim valve 98 is operableselectively engage the damper lock-out clutch 102. When the multiplexvalve 100 is in the spring set position, as shown in FIG. 2 a thepressurized fluid within the passage 96 will be directed to bias themotor/generator A cooling valve 64 and the motor/generator B coolingvalve 66 via a passage 103. The motor/generator A cooling valve 64 andthe motor/generator B cooling valve 66 operate to effect the cooling ofthe electrical power unit A 30 and the electrical power unit B 32,respectively, by varying the fluid flow from the main passage 54. Whenthe motor/generator cooling valves 64 and 66 are in the spring setposition, flow restrictors 105 and 105′, such as multiple orificeplates, restrict fluid flow to the electrical power units 30 and 32.Alternately when the motor/generator cooling valves 64 and 66 are in thepressure set position, the fluid flow rate will increase since thepressurized fluid within the main passage 54 can pass, unrestricted bythe flow restrictors 105 and 105′, to the electrical power units 30 and32.

The solenoid valve 82 is operable to provide an output pressure inpassage 104 that controls the bias pressure on a trim valve 106. Thesolenoid valve 84 is operable to provide an output pressure in passage108 that controls the pressure bias on a trim valve 110. The solenoidvalve 86 is operable to provide an output pressure in passage 112 thatcontrols the pressure bias on a trim valve 114. The solenoid valve 88 isoperable to provide an output pressure in passage 116 that controls thepressure bias on a trim valve 118. Additionally, the output pressure inpassage 116 controls the pressure bias on a boost valve 120. The trimvalves 106, 110, 114, and 118 are selectively biased into a secondposition or a pressure set position by fluid pressure within theirrespective passages 104, 108, 112, and 116. When the passages 104, 108,112, and 116 are de-pressurized, the respective trim valves 106, 110,114, and 118 move to a first position or a spring set position.Additionally, the trim valves 106, 110, 114, and 118 have a trim orpressure regulation position.

The solenoid valve 90 is operable to provide an output pressure inpassage 122 that controls the pressure bias on a logic valve 124. Theoutput pressure in passage 122 is also communicated to the trim valves106 and 118. The solenoid valve 92 is operable to provide an outputpressure that directly controls the pressure bias on a logic valve 126.The logic valve 126 has a differential area 127 operable to latch thelogic valve 126 in a pressure set position when the torque transmittingmechanism C2 is engaged and electrical power to the solenoid valve 92 isinterrupted. The logic valves 124 and 126 each have a first position ora spring set position, and a second position or a pressure set position.The solenoid valve 94 is operable to provide an output pressure inpassage 128 that controls pressure bias to the line regulator valve 56.The solenoid valve 94, by varying the pressure within passage 128, isoperable to vary the operating characteristics of the line regulatorvalve 56 thereby modulating the pressure value within the main passage54 for torque based pressure control.

When the hybrid vehicle is operating in a purely electric mode, anelectrically controlled hydraulic pump 130 is operable, in lieu of thehydraulic pump 50, to provide the electro-hydraulic control system 28with a pressurized fluid source. The electrically controlled hydraulicpump draws fluid from the reservoir 52 for delivery to a passage 132.The passage 132 is in fluid communication with and provides a controlpressure to bias the multiplex valve 100 into a pressure set position.Additionally, the passage 132 is in fluid communication with the damperlock-out clutch trim valve 98 and provides a pressurized source of fluidto selectively engage the damper lock-out clutch 102 when the damperlock-out clutch trim valve 98 is in a trim or pressure set position. Thepassage 132 is also in fluid communication with an electric moderegulator valve 134, which establishes the system pressure in thepassage 132 and when that pressure is satisfied, fluid is deliveredthrough passage 68 to the lubrication system 75 via the cooler 70 and/orbypass valve 72. Passage 136 is in fluid communication with check valves58 and 138.

A manual valve 140 receives pressurized fluid via a passage 142. Thepassage 142 is in selective fluid communication with either the mainpassage 54 or passage 136 depending on the position of the check valve58. The manual valve 140 has a neutral position, as shown in FIG. 2 b,and a drive position, as shown in FIGS. 3 b and 4 b. In the neutralposition, the manual valve 140 operates to block further communicationof pressurized fluid within passage 142. In the drive position, themanual valve 140 communicates the pressurized fluid within passage 142to a forward passage 144, which is in fluid communication with the trimvalves 114 and 118 and the logic valve 126. The pressurized fluid withinthe forward passage 144 is further directed to the trim valves 106 and110 by way of passage 145 when the logic valve 126 is controlled to thepressure set position, or when the logic valve 126 is latched in apressure set position by the torque transmitting mechanism C2.

The passage 76 is communicated with a backfill passage 146 through aflow restriction 148, such as orifices. The back fill passage 146communicates with a backfill check valve 150, which ensures that thepressure within the backfill passage 146 is maintained at a fixedpressure. The backfill passage 146 communicates with the trim valves106, 110, 114, and 118, the logic valves 124 and 126, the boost valve120, the manual valve 140, and the damper lock-out clutch trim valve 98.

The trim valve 106 selectively communicates pressurized fluid through anoutlet passage 152 to effect engagement of the torque transmittingmechanism C4. Likewise, the trim valve 110 selectively communicatespressurized fluid through an outlet passage 154 to effect engagement ofthe torque transmitting mechanism C3. An outlet passage 156 of the trimvalve 114 selectively communicates pressurized fluid to the logic valve126. The trim valve 118 selectively communicates pressurized fluid tothe boost valve 120 and the logic valve 124 through an outlet passage158. The logic valves 124 and 126 are in selective fluid communicationwith one another through passages 160 and 162.

Four pressure sensitive switches or pressure switches PS1, PS2, PS3, andPS4 are provided for position detection of the trim valves 106, 110,114, and 118 and the logic valves 124 and 126. The ability to monitorthe above mentioned valves and detect any change, or lack of change, invalve state is of importance to provide continuous and reliableoperation of the electrically variable hybrid transmission 14.

The electro-hydraulic control system 28 is capable of detecting statechanges of the trim valves 106, 110, 114, and 118 and the logic valves124 and 126 with the use of a multiplexed configuration of the fourpressure switches PS1, PS2, PS3, and PS4 disposed in selective fluidcommunication with the trim valves 118, 114, 110, and 106, respectively.Traditionally, six pressure switches, one switch for each valve, wouldhave been used to determine valve state changes. Detection of a statechange, or failure to change, of the logic valve 124 is achieved bymultiplexing the pressure switches PS1 and PS4. To achieve this, passage164 is disposed in fluid communication with the trim valves 106 and 118and the logic valve 124. The passage 164 is selectively pressurizedbased on the position of the logic valve 124. When the logic valve 124is in the spring set position, the passage 164 is pressurized with fluidfrom passage 76. Alternately, when the logic valve 124 is in thepressure set position, a land 172 blocks fluid communication with thepassage 76, therefore, the passage 164 is exhausted, as shown in FIG. 2b.

The passage 122 is disposed in fluid communication with the trim valves106 and 118 and the logic valve 124. When the solenoid valve 90 isenergized, the logic valve 124 moves to a pressure set position and thepassage 122 will pressurize. Alternately, when the solenoid valve 90 isde-energized, the logic valve 124 will move to a spring set position andthe passage 122 will exhaust. This multiplexed system provides areversal in states of pressurization between the passage 164 and 122.For example, if the logic valve 124 is in the pressure set position, thepassage 122 will be pressurized and the passage 164 will exhaust.Alternately, if the logic valve 124 is in the spring set position, thepassage 164 will be pressurized and the passage 122 will be exhausted.This event will be indicated through a change in logic state of both ofthe pressure switches PS1 and PS4 regardless of the position of theirrespective trim valves 118 and 106.

The detection of a state change, or failure to change, of the logicvalve 126 is achieved by multiplexing the pressure switch PS3. Toachieve this, a passage 168 is disposed in fluid communication with thetrim valve 110 and the logic valve 126. The pressure switch PS3 isselectively pressurized with fluid from the passage 76. When the logicvalve 126 is in the spring set position, the passage 168 is exhausted,thereby exhausting any pressurized fluid entering the trim valve 110from the passage 76. A series of orifices 170 is disposed within thepassage 76 to prevent the exhausting of the entire passage 76. Since nopressure builds within the trim valve 110, the pressure switch PS3 willreport a low logic state. Conversely, when the logic valve 126 moves toa pressure set position, the passage 168 is blocked disallowing anyexhaust flow from the passage 168. Pressurized fluid within the passage76 is now operable to change the logic state of the pressure switch PS3to high.

This multiplexed detection system operates in conjunction with therequired valve sequencing between the logic valve 126 and the torquetransmitting mechanisms C2 and C3 to effectively diagnose the state ofthe trim valve 110 and the logic valve 126 via pressure switch PS3. Foreffective torque transmitting mechanism actuation, the electro-hydrauliccontrol system 28 requires the logic valve 126 to be placed in apressure set position prior to placing the trim valve 110 in a pressureset position. The trim valve 110 may be placed in a pressure setposition with the logic valve 126 in a spring set position, however, thetorque transmitting mechanism C3 will continue to exhaust and remaindisengaged. Therefore, when the logic valve 126 is commanded to apressure set position, the trim valve 110 will be positioned to allowthe pressure switch PS3 to report a high logic state. With the logicvalve 126 is in a pressure set position, the pressure switch PS3 isoperable to diagnose the trim valve 110. If the torque transmittingmechanism C1 is commanded to engage by the logic valve 126, the pressureswitch PS3 should report a high logic value since the torquetransmitting mechanism C3 is not engaged at the same time that thetorque transmitting mechanism C1 engagement is commanded. Thus, if thepressure switch PS3 reports a low logic state, it is assumed that thetrim valve 110 has moved to a pressure set position and the appropriatediagnostic response is taken. For a condition where the torquetransmitting mechanism C2 is fed pressurized fluid by the logic valve126, the torque transmitting mechanism C3 may be engaged or disengageddepending on the current transmission range. However, with the torquetransmitting mechanism C2 pressurized, the logic valve 126 becomeslatched in the pressure set position. Therefore, all changes in logicstate of the pressure switch PS3 must be associated with the trim valve110. The above mentioned pressure switch logic can be applied toconditions where the pressure switch does not change logic statesindicating a stuck trim valve or logic valve.

FIGS. 2 a and 2 b shows the electro-hydraulic control system 28 in anelectrical power ON neutral mode of operation. In this mode, the logicvalve 124 is pressure set by energizing the solenoid valve 90, while thelogic valve 126 remains in the spring set position. By biasing the logicvalve 124 into the pressure set position, the electro-hydraulic controlsystem 28 is protected against a single point failure to range. Themanual valve 140 adds a redundant protection against a single pointfailure to range by blocking the pressurized fluid within the passage142 from entering the forward passage 144. The logic valves 124 and 126are operable to exhaust the torque transmitting mechanisms C1 and C2.The trim valves 106 and 110 are operable to exhaust the torquetransmitting mechanisms C3 and C4. Pressurized fluid within the passage76 communicates with the trim valve 114 to direct the pressure switchPS2 to report a high logic state for diagnostic purposes, while thepressure switches PS1, PS3, and PS4 will report a low logic state fordiagnostic purposes.

Additionally, the trim valves 106, 110, 114, and 118, the multiplexvalve 100, the motor/generator A cooling valve 64 and themotor/generator B cooling valve 66 remain in a spring set position forthis mode of operation. The lubrication system 75 will continue toreceive pressurized fluid by way of passage 68.

When operating in an engine OFF electric mode of operation, the internalcombustion engine 12, shown in FIG. 1, is shut off and the hybridvehicle will rely solely on the electrical storage device 44 to powerthe electrical power units 30 and 32 to effect movement of the vehicle.As a result, the hydraulic pump 50 will no longer provide a pressurizedsource of fluid within the main passage 54. Instead, the electricallycontrolled hydraulic pump 130 will provide fluid pressure to theelectro-hydraulic control system 28 via passage 132. The fluid pressurewithin the passage 132 will bias the multiplex valve 100 into a pressureset position. In this position, the solenoid 80 is operable to controlthe fluid pressure within the passage 99 via the passage 96. As aresult, the damper lock-out clutch trim valve 98 will bias to a trimposition allowing pressurized fluid within the passage 132 to effectengagement of the damper lock-out clutch 102. The damper lock-out clutch102 is operable to prevent the torsional resonance associated withstarting and stopping the engine 12 from being transmitted though thepowertrain 10. The multiplex valve 100 is pressure set only when theelectrically controlled hydraulic pump 130 is operating. Consequently,for each of the engine ON operating conditions the multiplex valve 100will remain in a spring set position.

Additionally, the pressurized fluid within passage 132 is communicatedto the electric mode regulator valve 134 placing it in a trim position.The electric mode regulator valve 134 will provide passage 68 with aregulated amount of fluid flow. This fluid will traverse the cooler 70and/or the cooler bypass valve 72 prior to entering the lubricationregulator valve 74, which provides regulated fluid pressure to thelubrication system 75. The line regulator valve 56 is in a spring setposition during the electric mode of operation, and is operable to blockthe flow of pressurized fluid within passage 68 from entering the mainpassage 54.

The electric mode regulator valve 134 will pass pressurized fluid frompassage 132 to passage 136. The fluid within passage 136 will unseat thecheck valve 138, which will allow fluid to pass into the passage 76. Thepassage 76 will distribute pressurized fluid to each of the solenoidvalves 82, 84, 86, 88, 90, 92, and 94 and the trim valve 110.Additionally, the actuator feed regulator 62, which is in a spring setposition, will allow fluid to pass from passage 76 into passage 78,which in turn provides pressurized fluid to the solenoid valve 80. Acheck valve 166 will prevent pressurized fluid within passages 76 and 78from entering the main passage 54.

The check valve 58 will allow pressurized fluid to pass from passage 136into the passage 142. The manual valve 140 will provide pressurizedfluid to the forward passage 144 when in the drive position, therebyproviding the electro-hydraulic control system 28 with a pressurizedsource of fluid to effect engagement of the torque transmittingmechanisms C1, C2, C3, and C4. The manual valve 140 will be in the driveposition for all operating conditions except neutral.

In the electric low speed mode of operation, the logic valve 124 ispressure set by energizing the solenoid valve 90 and the logic valve 126is pressure set by energizing the solenoid valve 92. The trim valve 118is pressure set by energizing the solenoid valve 88. The trim valves106, 110, and 114 remain in a spring set position. With the above statedvalve configuration, the torque transmitting mechanisms C2, C3, and C4will exhaust, while the torque transmitting mechanism C1 will engage. Toeffect engagement of the torque transmitting mechanism C1, pressurizedfluid from the forward passage 144 is communicated to the outlet passage158 of the trim valve 118. The logic valve 124 will communicate thefluid within the outlet passage 158 to the passage 160. The logic valve126 will communicate the pressurized fluid within the passage 160 to thetorque transmitting mechanism C1.

The pressurized fluid within the passage 76 communicates with the trimvalves 110 and 114 to direct the pressure switches PS3 and PS2,respectively, to report a high logic state for diagnostic purposes.Fluid pressure within passage 122 will direct the pressure switch PS1 toreport a high logic state. The pressure switch PS4 will report a lowlogic state for diagnostic purposes. Since the main passage 54 isdepressurized, the motor/generator cooling valves 64 and 66 will notprovide fluid flow to effect the cooling of the electrical power units30 and 32.

In the electric high speed mode of operation, the logic valve 124 is ina spring set position and the logic valve 126 is pressure set byenergizing the solenoid valve 92. The trim valve 114 is pressure set byenergizing the solenoid valve 86. The trim valves 106, 110, and 118remain in a spring set position. With the above stated valveconfiguration, the torque transmitting mechanisms C1, C3, and C4 willexhaust, while the torque transmitting mechanism C2 will engage. Toeffect engagement of the torque transmitting mechanism C2, pressurizedfluid from the forward passage 144 is communicated to the outlet passage156 of the trim valve 114, which is in fluid communication with thelogic valve 126. The logic valve 126 will communicate the pressurizedfluid within the outlet passage 156 to the torque transmitting mechanismC2.

Pressurized fluid within the passage 76 communicates with the trim valve110 to direct the pressure switch PS3 to report a high logic state fordiagnostic purposes. Additionally, pressurized fluid within the passage164 communicates with the trim valves 118 and 106 to direct the pressureswitches PS1 and PS4, respectively, to report a high logic state fordiagnostic purposes. The pressure switch PS2 will report a low logicstate for diagnostic purposes. Since the main passage 54 isdepressurized, the motor/generator cooling valves 64 and 66 will notprovide fluid flow to effect the cooling of the electrical power units30 and 32.

When operating in an electrically variable low speed mode of operation,the internal combustion engine 12 and the electrical power units 30 and32 work in concert to effect movement of the vehicle. This continuouslyvariable mode of operation employs the torque transmitting mechanism C1in conjunction with the electrical power units 30 and 32. All garageshifts, i.e. neutral to reverse, reverse to neutral, neutral to drive,and drive to neutral, are performed while in the electrically variable,low speed mode of operation. In this mode, the logic valve 124 ispressure set by energizing the solenoid valve 90 and the logic valve 126is pressure set by energizing the solenoid valve 92.

The trim valve 118 is pressure set by energizing the solenoid valve 88.The trim valves 106, 110, and 114 remain in a spring set position. Withthe above stated valve configuration, the torque transmitting mechanismsC2, C3, and C4 will exhaust, while the torque transmitting mechanism C1will engage. To effect engagement of the torque transmitting mechanismC1, pressurized fluid from the forward passage 144 is communicated tothe outlet passage 158 of the trim valve 118. The logic valve 124 willcommunicate the fluid within the outlet passage 158 to the passage 160.The logic valve 126 will communicate the pressurized fluid within thepassage 160 to the torque transmitting mechanism C1.

Pressurized fluid within the passage 76 communicates with the trimvalves 114 and 110 to direct the pressure switches PS2 and PS3,respectively, to report a high logic state for diagnostic purposes.Additionally, pressurized fluid within the passage 122 communicates withthe trim valve 118 to direct the pressure switch PS1 to report a highlogic state for diagnostic purposes. The pressure switch PS4 will reporta low logic state for diagnostic purposes.

The solenoid valve 80 will energize to provide fluid within the passage103 to bias the motor/generator A cooling valve 64 and themotor/generator B cooling valve 66. The pressurized fluid within thepassage 103 is operable to selectively place the motor/generator Acooling valve 64 and the motor/generator B cooling valve 66 in thepressure set position. The pressurized fluid within the main passage 54will effect cooling of the electrical power units 30 and 32 at varyingrates depending on the position of each of the motor/generator coolingvalves 64 and 66.

When operating in an electrically variable transmission high speed modeof operation, the internal combustion engine 12 and the electrical powerunits 30 and 32 work in concert to effect movement of the vehicle. Thiscontinuously variable mode of operation employs the torque transmittingmechanism C2 in conjunction with the electrical power units 30 and 32.The logic valve 126 is pressure set by energizing the solenoid valve 92,while the logic valve 124 remains in the spring set position.

The trim valve 114 is pressure set by energizing the solenoid valve 86.The trim valves 106, 110, and 118 remain in a spring set position. Withthe above stated valve configuration, the torque transmitting mechanismsC1, C3, and C4 will exhaust, while the torque transmitting mechanism C2will engage. To effect engagement of the torque transmitting mechanismC2, pressurized fluid from the forward passage 144 is communicated tothe outlet passage 156 of the trim valve 114, which is in fluidcommunication with the logic valve 126. The logic valve 126 willcommunicate the pressurized fluid within the outlet passage 156 to thetorque transmitting mechanism C2.

Pressurized fluid within the passage 164 communicates with the trimvalves 118 and 106 to direct the pressure switches PS1 and PS4,respectively, to report a high logic state for diagnostic. Additionally,pressurized fluid within the passage 76 communicates with the trim valve110 to direct the pressure switch PS3 to report a high logic state fordiagnostic purposes. The pressure switch PS2 will report a low logicstate for diagnostic purposes.

The solenoid valve 80 will energize to provide pressurized fluid withinthe passage 103 to bias the motor/generator A cooling valve 64 and themotor/generator B cooling valve 66. The pressurized fluid within thepassage 103 is operable to selectively place the motor/generator Acooling valve 64 and the motor/generator B cooling valve 66 in thepressure set position. The pressurized fluid within the main passage 54will effect cooling of the electrical power units 30 and 32 at varyingrates depending on the position of each of the motor/generator coolingvalves 64 and 66.

When operating in an electrically variable hill hold mode of operation,the logic valve 124 is pressure set by energizing the solenoid valve 90and the logic valve 126 is pressure set by energizing the solenoid valve92.

The trim valve 118 is pressure set by energizing the solenoid valve 88and the trim valve 110 is pressure set by energizing the solenoid valve84. The trim valves 106 and 114 remain in a spring set position. Withthe above stated valve configuration, the torque transmitting mechanismsC2 and C4 will exhaust, while the torque transmitting mechanisms C1 andC3 will engage. To effect the engagement of the torque transmittingmechanism C1, pressurized fluid from the forward passage 144 iscommunicated to the outlet passage 158 of the trim valve 118. The logicvalve 124 will communicate the fluid within the outlet passage 158 tothe passage 160. The logic valve 126 will communicate the pressurizedfluid within the passage 160 to the torque transmitting mechanism C1.Additionally, to effect the engagement of the torque transmittingmechanism C3, pressurized fluid from the forward passage 144 iscommunicated to the logic valve 126, which in turn will communicate thefluid to the passage 145. The passage 145 is in fluid communication withthe trim valve 110, which will subsequently pass the pressurized fluidinto the outlet passage 154 to the torque transmitting mechanism C3.

Pressurized fluid within the passage 76 communicates with the trim valve114 to direct the pressure switch PS2 to report a high logic state fordiagnostic purposes. Additionally, pressurized fluid within the passage122 communicates with the trim valve 118 to direct the pressure switchPS1 to report a high logic state for diagnostic purposes. The pressureswitches PS3 and PS4 will report a low logic state for diagnosticpurposes.

The solenoid valve 80 will energize to provide fluid within the passage103 to bias the motor/generator A cooling valve 64 and themotor/generator B cooling valve 66. The pressurized fluid within thepassage 103 is operable to selectively place the motor/generator Acooling valve 64 and the motor/generator B cooling valve 66 in thepressure set position. The pressurized fluid within the main passage 54will effect cooling of the electrical power units 30 and 32 at varyingrates depending on the position of each of the motor/generator coolingvalves 64 and 66.

When operating in the first forward range mode of operation, the logicvalve 124 is pressure set by energizing the solenoid valve 90 and thelogic valve 126 is pressure set by energizing the solenoid valve 92.

The trim valve 118 is pressure set by energizing the solenoid valve 88and the trim valve 106 is pressure set by energizing the solenoid valve82. The trim valves 110 and 114 remain in a spring set position. Withthe above stated valve configuration, the torque transmitting mechanismsC2 and C3 will exhaust, while the torque transmitting mechanisms C1 andC4 will engage. To effect the engagement of the torque transmittingmechanism C1, pressurized fluid from the forward passage 144 iscommunicated to the outlet passage 158 of the trim valve 118. The logicvalve 124 will communicate the fluid within the outlet passage 158 tothe passage 160. The logic valve 126 will communicate the pressurizedfluid within the passage 160 to the torque transmitting mechanism C1.Additionally, to effect the engagement of the torque transmittingmechanism C4, pressurized fluid from the forward passage 144 iscommunicated to the logic valve 126, which in turn will communicate thefluid to the passage 145. The passage 145 is in fluid communication withthe trim valve 106, which will subsequently pass the pressurized fluidinto the outlet passage 152 to the torque transmitting mechanism C4.

Pressurized fluid within the passage 76 communicates with the trimvalves 114 and 110 to direct the pressure switches PS2 and PS3,respectively, to report a high logic state for diagnostic purposes.Additionally, pressurized fluid within the passage 122 communicates withthe trim valves 118 and 106 to direct the pressure switches PS1 and PS4,respectively, to report a high logic state for diagnostic purposes.

The motor/generator A cooling valve 64 and the motor/generator B coolingvalve 66 are in the spring set position. Therefore, the pressurizedfluid within the main passage 54 will be supplied to effect the coolingof the electrical power units 30 and 32 at a reduced flow rate than whenthe motor/generator cooling valves 64 and 66 are in a pressure setposition. The motor/generator cooling valves 64 and 66 will remain inthe spring set position for each of the first, second, third, and fourthforward ranges.

When operating in the second forward range mode of operation, the logicvalve 124 is pressure set by energizing the solenoid valve 90 and thelogic valve 126 is pressure set by energizing the solenoid valve 92.

The trim valve 114 is pressure set by energizing the solenoid valve 86and the trim valve 118 is pressure set by energizing the solenoid valve88. The trim valves 106 and 110 remain in a spring set position. Withthe above stated valve configuration, the torque transmitting mechanismsC3 and C4 will exhaust, while the torque transmitting mechanisms C1 andC2 will engage. To effect the engagement of the torque transmittingmechanism C1, pressurized fluid from the forward passage 144 iscommunicated to the outlet passage 158 of the trim valve 118. The logicvalve 124 will communicate the fluid within the outlet passage 158 tothe passage 160. The logic valve 126 will communicate the pressurizedfluid within the passage 160 to the torque transmitting mechanism C1.Additionally, to effect the engagement of the torque transmittingmechanism C2, pressurized fluid from the forward passage 144 iscommunicated to the outlet passage 156 of the trim valve 114, which isin fluid communication with the logic valve 126. The logic valve 126will communicate the pressurized fluid within the outlet passage 156 tothe torque transmitting mechanism C2.

Pressurized fluid within the passage 76 communicates with the trim valve110 to direct the pressure switch PS3 to report a high logic state fordiagnostic purposes. Additionally, pressurized fluid within the passage122 communicates with the trim valve 118 to direct the pressure switchPS1 to report a high logic state for diagnostic purposes. The pressureswitches PS2 and PS4 will report a low logic state for diagnosticpurposes.

When operating in the third forward range mode of operation, the logicvalve 124 is pressure set by energizing the solenoid valve 90 and thelogic valve 126 is pressure set by energizing the solenoid valve 92.

The trim valve 106 is pressure set by energizing the solenoid valve 82and the trim valve 114 is pressure set by energizing the solenoid valve86. The trim valves 110 and 118 remain in a spring set position. Withthe above stated valve configuration, the torque transmitting mechanismsC1 and C3 will exhaust, while the torque transmitting mechanisms C2 andC4 will engage. To effect the engagement of the torque transmittingmechanism C2, pressurized fluid from the forward passage 144 iscommunicated to the outlet passage 156 of the trim valve 114, which isin fluid communication with the logic valve 126. The logic valve 126will communicate the pressurized fluid within the outlet passage 156 tothe torque transmitting mechanism C2. Additionally, to effect theengagement of the torque transmitting mechanism C4, pressurized fluidfrom the forward passage 144 is communicated to the logic valve 126,which in turn will communicate the fluid to the passage 145. The passage145 is in fluid communication with the trim valve 106, which willsubsequently pass the pressurized fluid into the outlet passage 152 tothe torque transmitting mechanism C4.

Pressurized fluid within the passage 76 communicates with the trim valve110 to direct the pressure switch PS3 to report a high logic state fordiagnostic purposes. Additionally, pressurized fluid within the passage122 communicates with the trim valve 106 to direct the pressure switchPS4 to report a high logic state for diagnostic purposes. The pressureswitches PS1 and PS2 will report a low logic state for diagnosticpurposes.

When operating in the fourth forward range mode of operation, the logicvalve 126 is pressure set by energizing the solenoid valve 92, while thelogic valve 124 remains in the spring set position.

The trim valve 110 is pressure set by energizing the solenoid valve 84and the trim valve 114 is pressure set by energizing the solenoid valve86. The trim valves 106 and 118 remain in a spring set position. Withthe above stated valve configuration, the torque transmitting mechanismsC1 and C4 will exhaust, while the torque transmitting mechanisms C2 andC3 will engage. To effect the engagement of the torque transmittingmechanism C2, pressurized fluid from the forward passage 144 iscommunicated to the outlet passage 156 of the trim valve 114, which isin fluid communication with the logic valve 126. The logic valve 126will communicate the pressurized fluid within the outlet passage 156 tothe torque transmitting mechanism C2. Additionally, to effect theengagement of the torque transmitting mechanism C3, pressurized fluidfrom the forward passage 144 is communicated to the logic valve 126,which in turn will communicate the fluid to the passage 145. The passage145 is in fluid communication with the trim valve 110, which willsubsequently pass the pressurized fluid into the outlet passage 154 tothe torque transmitting mechanism C3.

Pressurized fluid within the passage 164 communicates with the trimvalves 118 and 106 to direct the pressure switches PS1 and PS4,respectively, to report a high logic state for diagnostic purposes. Thepressure switches PS2 and PS3 will report a low logic state fordiagnostic purposes.

The electro-hydraulic control system 28 provides for controlled singlestep ratio interchanges in both an upshifting direction and adownshifting direction through engagement and disengagement ofrespective torque transmitting mechanisms when electrical power isavailable. Those skilled in the art will also recognize that theelectro-hydraulic control system 28 will permit skip shifting or doubleratio interchanges in the forward direction. A first forward range tothird forward range interchange is available by operating the trimvalves 118 and 114 to disengage the torque transmitting mechanism C1while engaging the torque transmitting mechanism C2. Alternately, athird forward range to first forward range interchange is available byoperating the trim valves 118 and 114 to engage the torque transmittingmechanism C1 while disengaging the torque transmitting mechanism C2.Additionally, a second forward range to fourth forward range interchangeis available by operating the trim valves 118 and 110 to disengage thetorque transmitting mechanism C1 while engaging the torque transmittingmechanism C3. Alternately, a fourth forward range to second forwardrange interchange is available by operating the trim valves 118 and 110to engage the torque transmitting mechanism C1 while disengaging thetorque transmitting mechanism C3.

If the electrical power to the electro-hydraulic control system 28 isinterrupted and the transmission is operating with the torquetransmitting mechanism C1 engaged, the electro-hydraulic control system28 will default to an electrical power OFF, electrically variable lowspeed mode of operation. In this mode, both logic valves 124 and 126 arein a spring set position since the solenoid valves 90 and 92 arenormally closed type valves.

The trim valves 114 and 118 will move to a pressure set position sincetheir respective solenoid valves 86 and 88 are normally open typevalves. The trim valves 106 and 110 will move to a spring set positionsince their respective solenoid valves 82 and 84 are normally closedtype valves. With the above stated valve configuration, the torquetransmitting mechanisms C2, C3, and C4 will exhaust, while the torquetransmitting mechanism C1 will engage. To effect engagement of thetorque transmitting mechanism C1, pressurized fluid from the forwardpassage 144 is communicated to the outlet passage 158 of the trim valve118. The logic valve 124 will communicate the fluid within the outletpassage 158 to the passage 162. The logic valve 126 will communicate thepressurized fluid within the passage 162 to the torque transmittingmechanism C1.

Pressurized fluid within the passage 164 communicates with the trimvalve 106 to direct the pressure switch PS4 to report a high logic statefor diagnostic purposes. The pressure switches PS1, PS2, and PS3 willreport a low logic state for diagnostic purposes.

The solenoid valve 80 is normally closed, and therefore, themotor/generator A cooling valve 64 and the motor/generator B coolingvalve 66 will remain in the spring set position, thereby allowing aminimal flow rate of fluid to effect cooling of the electrical powerunits 30 and 32. This condition will remain for both the electricalpower OFF low and high speed modes of operation.

Alternately, if the electrical power to the electro-hydraulic controlsystem 28 is interrupted and the transmission is operating with thetorque transmitting mechanism C2 engaged, the electro-hydraulic controlsystem 28 will default to an electrical power OFF, high speed mode ofoperation. In this mode, the logic valve 124 is in a spring set positionsince the solenoid valve 90 is a normally closed type valve. The fluidpressure within the torque transmitting mechanism C2 acting upon thedifferential area 127 will latch the logic valve 126 in the pressure setposition. This latched condition will occur when the torque transmittingmechanism C2 is engaged and electrical power is interrupted to thesolenoid valve 92. Additionally, the logic valve 126 will blockpressurized fluid within the passage 162 from engaging the toquetransmitting mechanism C1, thereby providing protection against aninadvertent torque transmitting mechanism C1 apply at high speeds.

The trim valves 114 and 118 will move to a pressure set position sincetheir respective solenoid valves 86 and 88 are normally open typevalves. The trim valves 106 and 110 will move to a spring set positionsince their respective solenoid valves 82 and 84 are normally closed.With the above stated valve configuration, the torque transmittingmechanisms C1, C3, and C4 will exhaust, while the torque transmittingmechanism C2 will engage. To effect engagement of the torquetransmitting mechanism C2, pressurized fluid from the forward passage144 is communicated to the outlet passage 156 of the trim valve 114,which is in fluid communication with the logic valve 126. The logicvalve 126 will communicate the pressurized fluid within the outletpassage 156 to the torque transmitting mechanism C2.

Pressurized fluid within the passage 164 communicates with the trimvalve 106 to direct the pressure switch PS4 to report a high logic statefor diagnostic purposes. The pressure switches PS1, PS2, and PS3 willreport a low logic state for diagnostic purposes. The passage 76communicates with the trim valve 110 to direct the pressure switch PS3to report a high logic state for diagnostic purposes.

While the best modes for carrying out the invention have been describedin detail, those familiar with the art to which this invention relateswill recognize various alternative designs and embodiments forpracticing the invention within the scope of the appended claims.

1. A pressure switch diagnostic system for an electrically variablehybrid transmission comprising: a plurality of trim valves each having afirst and a second position; a plurality of pressure sensitive switches,having a high and a low logic state, each in selective fluidcommunication with one of said plurality of trim valves; wherein each ofsaid plurality of pressure sensitive switches are operable to detect achange from said first to said second position or a change from saidsecond to said first position of its respective one of said plurality oftrim valves and accordingly each of said plurality of pressure switcheswill report one of said high or said low logic state; and at least onelogic valve in selective fluid communication with at least one of saidplurality of trim valves such that at least one of said plurality ofpressure sensitive switches are operative to detect changes in said atleast one logic valve without requiring an additional pressure sensitiveswitch to detect a change in position of said at least one logic valve.2. The pressure switch diagnostic system for an electrically variablehybrid transmission of claim 1, wherein a first of said at least onelogic valve has a first position and a second position and is disposedin selective fluid communication with a first and a second of saidplurality of trim valves respectively having a first and second of saidplurality of pressure sensitive switches in selective fluidcommunication therewith, said first and said second of said plurality ofpressure sensitive switches being operable to detect a change inposition of said first of said at least one logic valve when said firstof said at least one logic valve moves from said first to said secondposition or from said second to said first position irrespective of theposition of said first and second of said plurality of trim valves. 3.The pressure switch diagnostic system for an electrically variablehybrid transmission of claim 1, wherein a second of said at least onelogic valve, having a first position and a second position, is disposedin selective fluid communication with a third of said plurality of trimvalves having a third of said plurality of pressure sensitive switchesdisposed in selective fluid communication therewith, said third of saidplurality of pressure sensitive switches being operable to: detect achange in position of said second of said at least one logic valve fromsaid first position to said second position or said second position tosaid first position when said third of said plurality of trim valves isin said first position; and detect a change in position of said thirdtrim valve from said first position to said second position or saidsecond position to said first position when said second logic valve isin said second position.
 4. The pressure switch diagnostic system for anelectrically variable hybrid transmission of claim 1, wherein saidplurality of trim valves are solenoid operated pressure regulatorvalves.
 5. The pressure switch diagnostic system for an electricallyvariable hybrid transmission of claim 1, wherein said at least one logicvalve is a multiplex valve.
 6. The pressure switch diagnostic system foran electrically variable hybrid transmission of claim 1, wherein saidplurality of trim valves and said at least one logic valve areselectively controlled by an electronic control unit.
 7. The pressureswitch diagnostic system for an electrically variable hybridtransmission of claim 1, wherein said plurality of pressure sensitiveswitches selectively report said high and said low logic state to anelectronic control unit.
 8. A pressure switch diagnostic system for anelectrically variable hybrid transmission comprising: a first trimvalve, having a first position and a second position, in selective fluidcommunication with a first pressure sensitive switch, wherein said firstpressure sensitive switch is operable to detect and report a change fromsaid first to said second position or said second to said first positionof said first trim valve; a second trim valve, having a first positionand a second position, in selective fluid communication with a secondpressure sensitive switch, wherein said second pressure sensitive switchis operable to detect and report a change from said first to said secondposition or said second to said first position of said second trimvalve; a third trim valve, having a first position and a secondposition, in selective fluid communication with a third pressuresensitive switch, wherein said third pressure sensitive switch isoperable to detect and report a change from said first to said secondposition or said second to said first position of said third trim valve;a first logic valve, having a first position and a second position,disposed in selective fluid communication with each of said first trimvalve and said second trim valve; and a second logic valve, having afirst position and a second position, disposed in selective fluidcommunication with said third trim valve. wherein said first, second,and third trim valves and said first, second, and third pressuresensitive switches and said first and second logic valve are connectedin a multiplexed arrangement such that there are fewer of said pressuresensitive switches than the sum of said trim valves and said logicvalves.
 9. The pressure switch diagnostic system for an electricallyvariable hybrid transmission of claim 8, wherein said first pressuresensitive switch and said second pressure sensitive switch is operableto detect a change from said first to said second position or saidsecond to said first position of said first logic valve irrespective ofthe position of said first trim valve and said second trim valve. 10.The pressure switch diagnostic system for an electrically variablehybrid transmission of claim 8, wherein said third pressure sensitiveswitch is operable to detect a change from said first to said secondposition or said second to said first position of said second logicvalve when said third trim valve is in said first position.
 11. Thepressure switch diagnostic system for an electrically variable hybridtransmission of claim 8, wherein said third pressure sensitive switch isoperable to detect a change from said first to said second position orsaid second to said first position of said third trim valve when saidsecond logic valve is in said second position.
 12. The pressure switchdiagnostic system for an electrically variable hybrid transmission ofclaim 8, wherein said first, second, and third trim valves are solenoidoperated pressure regulator valves.
 13. The pressure switch diagnosticsystem for an electrically variable hybrid transmission of claim 8,wherein said first and second logic valve are multiplex valves.
 14. Thepressure switch diagnostic system for an electrically variable hybridtransmission of claim 8, wherein said first, second, and third trimvalves and said first and second logic valves are selectively controlledby an electronic control unit.
 15. The pressure switch diagnostic systemfor an electrically variable hybrid transmission of claim 8, furthercomprising: a fourth trim valve, having a first position and a secondposition, in selective fluid communication with a fourth pressuresensitive switch, wherein said first pressure sensitive switch isoperable to detect and report a change from said first to said secondposition or said second to said first position of said fourth trimvalve.
 16. A pressure switch diagnostic system for an electricallyvariable hybrid transmission comprising: a first trim valve, having afirst position and a second position, in selective fluid communicationwith a first pressure sensitive switch, wherein said first pressuresensitive switch is operable to detect and report a change from saidfirst to said second position or said second to said first position ofsaid first trim valve; a second trim valve, having a first position anda second position, in selective fluid communication with a secondpressure sensitive switch, wherein said second pressure sensitive switchis operable to detect and report a change from said first to said secondposition or said second to said first position of said second trimvalve; a third trim valve, having a first position and a secondposition, in selective fluid communication with a third pressuresensitive switch, wherein said third pressure sensitive switch isoperable to detect and report a change from said first to said secondposition or said second to said first position of said third trim valve;a fourth trim valve, having a first position and a second position, inselective fluid communication with a fourth pressure sensitive switch,wherein said first pressure sensitive switch is operable to detect andreport a change from said first to said second position or said secondto said first position of said fourth trim valve; a first logic valve,having a first position and a second position, disposed in selectivefluid communication with each of said first trim valve and said secondtrim valve; a second logic valve, having a first position and a secondposition, disposed in selective fluid communication with said third trimvalve; wherein said first pressure sensitive switch and said secondpressure sensitive switch are operable to detect a change from saidfirst to said second position or said second to said first position ofsaid first logic valve irrespective of the position of said first trimvalve and said second trim valve; wherein said third pressure sensitiveswitch is operable to detect a change from said first to said secondposition or said second to said first position of said second logicvalve when said third trim valve is in said first position; and whereinsaid third pressure sensitive switch is operable to detect a change fromsaid first to said second position or said second to said first positionof said third trim valve when said second logic valve is in said secondposition.
 17. The pressure switch diagnostic system for an electricallyvariable hybrid transmission of claim 16, wherein said first, second,third, and fourth trim valves are solenoid operated pressure regulatorvalves.
 18. The pressure switch diagnostic system for an electricallyvariable hybrid transmission of claim 16, wherein said first and secondlogic valve are multiplex valves.
 19. The pressure switch diagnosticsystem for an electrically variable hybrid transmission of claim 16,wherein said first, second, third, and fourth trim valves and said firstand second logic valve are selectively controlled by an electroniccontrol unit.